Thermally actuable means for operating electric switches



Nov. 27, 1934. D w JOHNSON 1,982,521

THERMALLY ACTUABLE MEANS FOR OPERATING ELECTRIC SWITCHES Filed Aug. 17, 1952 INVENTOR DAVID W.JOHNSON BY HIS ATTORNEYS Patented Nov. 27, 1934 TUNITED STATES PATENT OFFICE THERMALLY ACTUABLE MEANS FOR OPERATING ELECTRIC SWITCHES David W. Johnson, New Britain, Conn., assignor to The Arrow-Hart & Hegeman Electric Company, Hartford, Conn necticut a corporation of Con- Application August 17, 1932, Serial No. 629,224 6 Claims. (c1. 200-116) This invention relates to means operable upon overload for causing automatic operation of electric switches. More particularly, it relates to devices of this kind which are caused to operate by heat generated by reason of an excessive current or overload.

It is an object of my invention to provide a simplified device of the above type which may be quickly and economically manufactured.

Another object of my invention is to provide a device of the above type which will be more accurate in operation by reason of reduced friction incident to the operation thereof.

Other objects and advantages of my invention ll will appear as it is described in connection with the accompanying drawing.

In the drawing:---

Figure 1 is a side elevation view of my invention as applied to a circuit breaker.

Figure 2 is a longitudinal section view inelevation of my invention.

Figure 3 is a view similar to Figure 2, but showing the parts of the invention in the position they take after an excess current has caused :5 operation thereof. 1

Figure 4 is a plan view of the invention as shown in Figures 2 and 3.

Figure 5 is a bottom view of the invention shown in Figures 2, 3 and 4.

Figure 6 is atransverse section taken 6-6 of Figure2.

Referring to the drawing, my invention is shown when used with a circuit breaker 8 of the type shown in the copending application of Monroe Guett, Serial No. 589,907 but it may be used with many other switches which are capable of operating when an overload occurs. 7 My invention is secured upon the switch'base 10, in any suitable manner and comprises a sup-' 0 port 12 formed from a rectangular plate of sheet metal stamped to provide a lengthwise-extending central channel 14. A movable tripping member in the form of a flat bar 16 of metal, whose width is approximately that of the channel 14 and. whose length is greater than that of the support 12, is slidable in the channel 14, and is guided by the channel surfaces or walls. Lateral extensions 17 from each edge of one end (which for convenience will be called the rear end) of the tripping 5 bar 16 slide within slots 18 cut in the parallel side walls of the channel 14 at one end of the support 12. On the other end of the support is mounted a T-shaped bimetallic thermal bar 20 whose transverse portion 20a bridges the channel 14 at the end of the support and is secured to so on line the support in any suitable fashion as by rivets 22. The thermal bar 20 extends toward the end opposite to which it is secured, to a point beneath a pair of registering apertures 21, 23 forined in the rear central portions of the support 12 and bar 16. The lateral extensions 17 and the thermal bar 20 while permitting movementof the tripping bar 16 in the direction of its length, hold it from falling out of the channel 14.

In order to urge the tripping bar 16 forward, a 35 tension coil spring 24 has one of its ends secured to a finger 26 bent up perpendicular to the trip ping bar 16 at its rear end, the other end of the spring is hooked around a stationary screw bolt 27 passing through the thermal bar 20 a slot 25 in tripping bar 16, and through the support 12 near its front end. In order to hold the tripping bar against the urge of spring 24 a ball 28 whose diameter is slightly less than that of the apertures 21, 23 so that the ball may move freely 78 therein, is positioned in the apertures. A leaf spring 30 which is secured upon the support 12 by the nut 29 on the bolts 27 holds the ball within the apertures. The end of the leaf spring 30 is provided with an indentation or aperture 31 providing a seat for the ball.

The base 10 has a recess 32 therein beneath the thermal bar 20 in which recess is positioned a coil 34 or other device which heats up upon the passage through it of an excess current. This coil is connected in series .in circuit with the switch. Upon occurrence of an overload the heat of the coil 34 causes the thermal bar 20 to bend engaging the ball 28 and forcing it, against the action of the leaf spring 30,,out of the aperture 31 in the tripping bar 16, thereby permitting the tripping bar 16 to move forward in the direction of its length to engage the toggle lever 36 and cause the switch 8 to move automatically to open circuit position.

The use of the ball 28 as an anti-friction latch- 7 ing means is advantageous since it makes possible 2. more accurate operation of the switch due to the reduction in the friction. The invention may be inexpensively constructed from sheet metal for the most part and is not likely to get out of order. The simplicity and ruggedness of its construction will be readily appreciated by those skilled in the art.

Many variations and changes within the scope of my invention will occur to those skilled in the art, therefore I do not limit the invention to the specific embodiment shown in the drawing.

I claim:-

1. A tripping device for electric switches comprising supporting means having guiding surfaces, spring urged means guided by said surfaces and movable in the direction of its length, antifriction latching means engaging with said supporting means and said spring urged means, and self restoring thermally actuated means for moving said latching means to release said spring urged means.

prising supporting means having a channel,

spring urged means movable longitudinally of said channel, anti-friction latching means engaging with said supportingineans and said spring urged means, and self-restoring thermally actuated means for moving said latching means to release said spring urged means.

4. A tripping device for electric switches comprising supporting mean's having guiding surfaces, spring urged means guided by said surfaces and movable in the direction of its length, a ball latch engaging with said supporting means and said spring urged means, and self restoring thermally actuated means for moving said ball to release said spring urged means.

5. A tripping device for electric switches comprising supporting means havinga recess therein, means normally urged in the direction of its length and having a recess therein, a ball latch in said recesses, and self restoring thermally actuated means for moving said ball to release said urged means.

6. A tripping device for electric switches comprising supporting means having a recess therein, means normally urged in the direction of its length and having a recess therein, a ball latch in said recesses, and self restoring thermally actuated means for moving said ball in a direction perpendicular to the plane of said urged means to release said urged means.

DAVID W. JOHNSON 

